Introduce the PlatformNotificationContext class.

content/browser/notifications/platform_notification_context.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_BROWSER_NOTIFICATIONS_PLATFORM_NOTIFICATION_CONTEXT_H_
+#define CONTENT_BROWSER_NOTIFICATIONS_PLATFORM_NOTIFICATION_CONTEXT_H_
+
+#include <stdint.h>
+
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "content/common/content_export.h"
+
+class GURL;
+
+namespace base {
+class SequencedTaskRunner;
+}
+
+namespace content {
+
+class NotificationDatabase;
+struct NotificationDatabaseData;
+
+// Implementation of the Web Notification storage context.
+//
+// Represents the per-BrowserContext data for persistent Web Notifications.

[johnme, 2015/03/16 16:54:43]

http://goo.gl/TciXVp says it's per-StoragePartitionImpl not per-BrowserContext.
Which is it?

[Peter Beverloo, 2015/03/16 17:55:01]

It's per storage partition. Amended.

+// The methods defined in this interface must only be called on the IO thread.

[johnme, 2015/03/16 16:54:43]

Except OpenDatabase, DoRead and DoWrite. Add "unless otherwise specified"?

[Peter Beverloo, 2015/03/16 17:55:01]

Changed it to "The public methods" instead.

+class CONTENT_EXPORT PlatformNotificationContext
+    : public base::RefCountedThreadSafe<PlatformNotificationContext> {
+ public:
+  // Constructs a new platform notification context. If |path| is non-empty, the
+  // database will be initialized in the "Platform Notifications" subdirectory
+  // of |path|. Otherwise, the database will be initialized in memory.
+  explicit PlatformNotificationContext(const base::FilePath& path);
+
+  using ReadResultCallback =
+      base::Callback<void(bool /* success */,

[johnme, 2015/03/16 16:54:43]

Nit: you don't need to comment out the parameter names (ditto below).

[Peter Beverloo, 2015/03/16 17:55:01]

Technically I don't, but If I read "base::Callback<void(bool, int64_t)>" I don't
know what I'm going to get. I include them for readability purposes.

+                          const NotificationDatabaseData&)>;
+
+  using WriteResultCallback =
+      base::Callback<void(bool /* success */,
+                          int64_t /* notification_id */)>;
+
+  // Reads the data associated with |notification_id| belonging to |origin|
+  // from the database. |callback| will be invoked with the success status
+  // and a reference to the notification database data when completed.
+  void ReadNotificationData(int64_t notification_id,
+                            const GURL& origin,
+                            const ReadResultCallback& callback);
+
+  // Writes the data associated with a notification to a database. When this
+  // action completed, |callback| will be invoked with the success status and
+  // the persistent notification id when written successfully.
+  void WriteNotificationData(const GURL& origin,
+                             const NotificationDatabaseData& database_data,
+                             const WriteResultCallback& callback);
+
+ private:
+  friend class base::RefCountedThreadSafe<PlatformNotificationContext>;
+  friend class PlatformNotificationContextTest;
+
+  virtual ~PlatformNotificationContext();
+
+  // Initializes the database if neccesary. Must be called on the IO thread.
+  // |success_closure| will be invoked on a the |task_runner_| thread when
+  // everything is available, or |failure_closure_| will be invoked on the
+  // IO thread when initialization fails.
+  void LazyInitialize(const base::Closure& success_closure,
+                      const base::Closure& failure_closure);
+
+  // Opens the database. Must be called on the |task_runner_| thread. When the
+  // database has been opened, |success_closure| will be invoked on the task
+  // thread, otherwise |failure_closure_ will be invoked on the IO thread.

[johnme, 2015/03/16 16:54:43]

Nit: |failure_closure_|

[Peter Beverloo, 2015/03/16 17:55:01]

Done.

+  void OpenDatabase(const base::Closure& success_closure,
+                    const base::Closure& failure_closure);
+
+  // Actually reads the notification data from the database. Must only be
+  // called on the |task_runner_| thread. Will post a task to |callback| on
+  // the IO thread when the operation has completed.
+  void DoReadNotificationData(int64_t notification_id,
+                              const GURL& origin,
+                              const ReadResultCallback& callback);
+
+  // Actually writes the notification database to the database. Must only be
+  // called on the |task_runner_| thread. Will post a task to |callback| on
+  // the IO thread when the operation has completed.
+  void DoWriteNotificationData(const GURL& origin,
+                               const NotificationDatabaseData& database_data,
+                               const WriteResultCallback& callback);
+
+  // Returns the path in which the database should be initialized. May be empty.
+  base::FilePath GetDatabasePath() const;
+
+  // Sets the task runner to use for testing purposes.
+  void SetTaskRunnerForTesting(
+      const scoped_refptr<base::SequencedTaskRunner>& task_runner);
+
+  base::FilePath path_;
+
+  scoped_refptr<base::SequencedTaskRunner> task_runner_;
+  scoped_ptr<NotificationDatabase> database_;
+
+  DISALLOW_COPY_AND_ASSIGN(PlatformNotificationContext);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_NOTIFICATIONS_PLATFORM_NOTIFICATION_CONTEXT_H_